leak metering gas lifted wells - alrdc

Feb. 4 – 8, 2013 2013 Gas-Lift Workshop 1

Leak Metering Gas Lifted Wells

• Morten Kvernvold, MD

• ScanWell AS

36th Gas-Lift Workshop Stavanger, Norway February 4 – 8, 2013


Challenges

Well Integrity Failures

• According to PSA a conventional

well, which is converted to gas lift,

will experience well integrity failures

within two years of production.


Challenges

Optimizing Production

• Gas lift hides

innefficiencies

• Without regular

surveillance, gas lift

wells are far less likely

to produce at optimal

levels.


Risk Assessment

2007 – PSA & Sintef finds well integrity issues

on 25% of the well on the NCS.

PSA & OGN Guideline 117 (2007) - Evaluation

– 4.2.1 Source, mechanism and location of leaks

– 4.2.2 Leak rate

– 4.2.3 Annulus pressure

– 4.2.4 Hydrocarbon gas volume and mass

– 4.2.5 Escalation potential

New guidelines and redesigned audits have reduced

the number of red/orange wells to 8.6% in 2012.

Identifying & Understanding SCP

Feb. 4 – 8. 2013 2013 Gas-Lift Workshop

5

Requires custom designed equipment & competency

• Dependancy between pressure (communication)

• Fluid analysis to establish source of pressure increase

• Fluid analysis to monitor corrosive and hazardous components

• Gas volume and hydrocarbon mass evaluation

• Direct measurements of gas and liquid leak rates

• Quantify liquid influx into gas filled volumes

• Identify location of leaks and leak paths

• Potential annulus pressures vs. MAASP

• Escalation potential

6

Leak Metering System (LMS)

LMS Dim:100x65x85cm

Weight: 150 kg

Rating: 35 MPa / 200 °C

Applied for:

- Direct leak metering

- Leak properties

- Leak composition

- Toxic and corrosive

- Volume & mass

- Wireless pressure

ATEX zone 1

approved

No intervention is

required.

7

Acoustic Metering System (AMS)

• ATEX Zone 1 approved

• Battery operated

• Less than 100 kilos

Connection to well

Pressure rating: 15000 psi

Mounting: Tubing or annuli

Maximum depth: 6000 m (?)

Applied for:

- Determination of gas volumes in annulus

- Determine liqiuid influx during inflow test

- Determine anomalies in tubing or casing

- Determination of reservoir pressure

8

Trace Metering System (TMS)

WellTracer® Equipment Rating: Class I

Division 2 Groups A, B, C, D with a Type Z

purge also suitable for use in Class I Zone 2

AEx pZ IIC; Ex pZ IIC; T6 for use in

hazardous areas

Applied for:

- Determine depth of leaks in tubing or casing

- Gas lift surveillance & troubleshooting

- Determine relative size of leaks

9

A A

B B

TBG

Rigup for leak test and gas lift surveillance

Activity Time required

1. Rig up on well 1 hrs

2. Measure initial gas volume 0.5 hrs

3. Gas compositional analysis 1 hrs

4. Shoot liquid level 0.5 hrs

5a. Bleed down 0.1-1 hrs

5b. Inject CO2 tracer 0.1 hrs.

6. Measure gas leak rate 0.1-1 hrs


8. Pressure buildup test 1-6 hrs


10. Calculate liquid leak rate 1 hrs

Sum – Time of activities 6-12 hrs

Gas-lift

CO2 inj.

10

Leak metering Gas Lift Valve (GLV)

Leak rate is measured while bleeding down.

Only a partial bleed down is required

Maximum leak rate is recorded at sonic flow

Liquid influx is detected by acoustics

Communication is spotted by wireless.

Online gas chromatography to determine

gas composition & properties.

Pressure buildup analysis.

• Reduced time

• Less stress on casing/cement

• Improved data quality

• Third party verification

• Reduced workload for onsite personnel

A A

B B

TBG

1) Initial conditions Initial pressure, depth of gas-liquid interface, gas volume, fluid density, gas composition

2) Bleed down test Plot showing pressure, temperature, flow rate and density measured during bleed down

Plot showing pressure response in tubing and all annuli used to determine communication

Total volume (mass) taken out during test

Gas volume calculation based on pressure drop and volume taken out

3) Leak rate test Plot showing pressure, density, temperature and flow rate

Measured leak rate of gas and liquid, pressure, density, temperature

4) Pressure buildup test Plot showing pressure in tubing and annuli during test

Pstart - Pfinal, Gas volume (start/final), Calculated leak rate

5) Diagnostic test Acoustic determination of leak points

Pressure and liquid level manipulation to determine depth of leaks (u-tube calculations)

TMS (WellTracer) survey to determine depth of leaks in tubing and casing


11

Sequence of measurements

Determination of liquid level and gas volume

Monitoring liquid influx

Acoustic measurements of the

gas-liquid contact is performed

during the bleed down period.

Movements in the liquid level is

used to determine liquid leak

rate.

Determination of gas leak rate

Monitoring gas influx

The LMS system monitors

the maximum gas leak rate.

Fluid properties and

composition is also

monitored by the LMS.

Determination of leak depth

Using TMS / WellTracer ®

• The depth of leaks in tubing is

determined by injecting a tracer

component into the lift gas while the

well is producing normally

• The exact depth of the leaks is

determined using downhole

reference points.

• Injection through the failed gas lift

valve in the top mandrel is wasting

37% of the lift gas resulting in a 21

bbls/day lost of oil production.

Gas lift surveillance


15

WellTracer for Surveillance and Production optimization

• Detect inefficiencies

• Monitor injection points

• Monitor lift gas rates

• Optimize well performance

• Verify gas lift design

Detecting problems at an early stage


16

Life-cycle approach

• PERSON/PATIENT

– Genes

– Brain / impulses

– Health check

– Diagnosis

– Medication

– Surgery

– Dead

• WELL

– Well construction

– Intrumentation

– PM program

– Diagnostic measurements

– Chemicals/Cleaning

– Intervention/Workover

– P & A



17

Life-cycle approach

• PERSON/PATIENT

– Genes


– Health check

– Diagnosis

– Medication

– Surgery

– Dead

• WELL


– Intrumentation

– PM program




– P & A

LMS/AMS/TMS



18

Importance of Preventive Maintenance routines (PM)

• PERSON/PATIENT

– Genes


– Health check

– Diagnosis

– Medication

– Surgery

– Dead

• WELL


– Intrumentation

– PM program




– P & A Sudden death

Serious incident

Experience from GLV testing on the NCS

560 GLV’s tested in 2012.

73 GLV’s leaking outside API

criteria.

63 GLV’s successfully cleaned

(86%).

Lifetime of GLV on average

extended by almost two years,

compared to changing valve

on first leak test failure.

Production Reducing Activities (PRA)

Start PRA/PM01

Permit & SJA

Pressure test equipment Inflow test AWV

Shut in well at surface

Inflow leak test Xmas tree valves

Inflow leak test DHSV

With zero pressure above DHSV, start wellhead maintenance

Flow line inspection

Equalize pressure and reopen DHSV

Pressure up tubing

Measure liquid level in tubing

Shut down gas lift

Inflow leak test ASV valve

Inflow leak test ESD valve

Reopen ASV valve

Measure fluid level and calculate gas volume

Leak test ASCV og HASCV.

Bleed down for inflow test of GLV

Measure leak rate in GLV

Restart well.

Optimizing PRA’s

• Wellhead maintenance

• Flowline inspections

• Well integrity surveys

By synchronizing such activities

the number of planned shutdowns

can be significantly reduced,

leading to increased yearly

production

Summary

• Well Integrity & Gas lift

performance can be tested

with one simple survey.

• No intervention is required

for a standard test.

• No production shutdown is

required when performing

gas lift surveillance.

• Only a partial bleed down is

required for leak testing.

THANK YOU!

Questions?


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leak metering gas lifted wells - alrdc

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